Choose the answer among A, B, C, D to complete each of the sentences below:
About 100 Russian satellites are _____ the earth.
A.traveling
B.circuiting
C.orbitting
D.flying

Choose the answer among A, B, C, D to complete each of the sentences below:
A nuclear reactor releases ______ which is dangerous to the environment.
A.heat
B.carbon dioxide
C.energy
D.radiation

Choose the answer among A, B, C, D to complete each of the sentences below:
In 1987, the Great Wall was listed as a World Heritage _____ UNESCO.
A.of
B.to
C.by
D.with

Choose the answer among A, B, C, D to complete each of the sentences below:
Pressure on natural resourses will _______ as we face a population explosion.
A.decrease
B.increase
C.decline
D.raise

Choose the answer among A, B, C, D to complete each of the sentences below:
In spite of all its ______, medical science knows little about the brain.
A.advances
B.advents
C.advantages
D.approaches

Choose the answer among A, B, C, D to complete each of the sentences below:
I felt my face burning with ________.
A.confidence
B.enthusiasm
C.embarrassment
D.pleasure

Choose the answer among A, B, C, D to complete each of the sentences below:
Many newer cars have a much lower fuel ______.
A.consumer
B.consuming
C.consumation
D.consumption

Choose the answer among A, B, C, D to complete each of the sentences below:
He built _____ his collection over a period of ten years.
A.up
B.on
C.into
D.in

Choose the answer among A, B, C, D to complete each of the sentences below:
If you want to send a document and do not want to lose, its original shape, our _____ service will help you.
A.messenger call
B.express mail
C.postal
D.facsimile

Choose the answer among A, B, C, D to complete each of the sentences below:
The Great Wall is China's most popular ______.
A.contribution
B.construction
C.attraction
D.impression